Effects of different salinity levels and carbon sources in biofloc production system

      Carbonaceous organic matter and water salinity are the key factors in zero water exchange system with biofloc production. In thepresent study, production of biofloc in different water salinities and carbon sources was investigated in zero water exchange system. For this purpose, three levels of salinity (10, 21 and 32 ppt) and two types of carbon source (molasses and wheat flour)were considered in zero water exchange system. The experiment was conducted in tanks with water volume of 300L for 4 weeks in propagation and cultivation aquatics center located in Bandar Kolahi, Minab, Hormozgan province. Minimum dissolved oxygen (5.68 mg/l) and NH₃ (0.29 mg/l) and maximum NO₃ (12.68 mg/l) obtained in the tanks with molasses, as carbon source, and 32ppt water salinity. Some of water phsicochemical parameters including dissolved oxygen, pH, NH₃ and NO₃ were measured regularly and significant differences were observed among the different treatments (p<0.05). The analysis of the biochemical composition of the bioflocs showed a decrease in protein and an increase in ash content along with increase in water salinity. Lipid content in molass biofloc was significantly lower than the wheat flour biofloc (p<0.05). The results showed that type of carbon source and value of salinity would be effective on water quality parameters and nutrition value of bioflocs in zero water exchange system.